Image Tamper Detection Based on Logistic Map and Block Average

Abstract

Intruders can tamper the medical images while it is on transit in internet. So, various tamper detection techniques came into existence. Mainly the earlier research on watermarking focused on embedding the watermark, and extracting the water mark. Recently, tamper detection is also considered as a necessary task for any efficient watermarking mechanism. This article proposes a tamper identification scheme using the concept of blocks. In a block of 4×4 pixels, there exists 16 pixels, their LSBs are set to zeroes. Then the mean pixel value of a block is enumerated. These 8 binary bits of mean value is hidden in LSBs of upper half (UH) of the block. Furthermore, an 8-bit key value is generated from logistic map (LM). The binary value of block mean and key value are XORed to compute the watermark bits (WBs). These bits are hidden in LSBs of the lower half (LH) of the block. At the receiver side the block mean is computed and made XOR operation with the 8-bit key value created from LM. These are the computed WBs(CWBs). The 8 bits from the LSBs of the pixels of UH of the block are extracted. WBs are extracted from the LH of the block. If the CWBs are same as the extracted WBs and computed block mean is same as the extracted bits from UH of the block, then the block is earmarked as not tampered. The merit of this methodology is enumerated by various quality parameters. The values of these parameters are improved as compared to the related existing literature.